A little over two weeks into November, the Capital has already seen nine ‘severe’ air days — three times the figure recorded last year when three such days were witnessed all through the month. Delhi’s AQI on Friday was 405, in the ‘severe’ category (401 to 500), only marginally less than the 419 recorded Thursday. The AQI first slipped into the ‘severe’ category on November 2. The Air Quality Early Warning System for Delhi indicates that the air quality is likely to remain ‘very poor’ from November 18- 20. In November 2021, Delhi saw 11 ‘severe’ air days. Before that, there were 9 such days in 2020, 7 days in 2019, and 5 days in 2018, going by Central Pollution Control Board bulletins. With winds mostly coming from the east of Delhi, contribution of stubble burning to PM 2.5 levels was estimated to be low on Friday, likely to be only around 3.45%, according to the Indian Institute of Tropical Meteorology’s Decision Support System. This is a little less than the 5.85% contribution of stubble burning to PM 2.5 levels on Thursday. So far this season, this contribution has peaked at 35.43% on November 3. Winds are likely to be from the east or southeast of Delhi over the next two days as well, going by the early warning system forecast. Winds from the north and northwest are usually favourable for bringing stubble burning smoke into Delhi. IIT Kanpur’s real-time source apportionment study for Delhi estimated vehicles to be the single largest contributor to PM 2.5 levels Friday at 44%, up from 27% Thursday, and 38% Wednesday. The study, which uses data collected from a supersite near Rouse Avenue, found that the contribution of vehicles to PM 2.5 levels peaked at 90% at 9 am Friday, and fell to around 47% at 3 pm. A senior official in the Delhi Pollution Control Committee said focus remains on enforcing existing restrictions under stage-IV of the Graded Response Action Plan, including ban on construction and demolition activities, and checking pollution under control certificates. Meanwhile, after hearing a matter on air pollution in Delhi on November 8, the National Green Tribunal directed that “stringent measures” be enforced in the city and an action-taken report filed by November 20.
